Reflections visible in Vieweport but Flat/Barely noticeable in final render
Your scene environment is not set up properly. The HDRI is using an ordinary Image Texture node, not an Environment Texture node:

Deleting it and replacing it with an Environment Texture node fixes the render:

The reason the result looks okay in the 3D viewport is because it looks like you had Scene World unchecked in the scene options:

If you check that box, then the 3D viewport matches the rendered result.